A human auditory system includes an outer ear, middle ear, and inner ear. With the outer ear, middle ear, and inner ear, the human auditory system is able to hear sound. For example, a sound source such as a loudspeaker in a room may output sound. A pinna of the outer ear receives the sound, directs the sound to an ear canal of the outer ear, which in turn directs the sound to the middle ear. The middle ear of the human auditory system transfers the sound into fluids of an inner ear for conversion into nerve impulses. A brain then interprets the nerve impulses to hear the sound. Further, the human auditory system is able to perceive the direction where the sound is coming from. The perception of direction of the sound source is based on interactions with human anatomy. The interaction includes the sound reflecting and/or reverberating and diffracting off a head, shoulder and pinna. The interaction generates audio cues which are decoded by the brain to perceive the direction where the sound is coming from.
It is now becoming more common to listen to sounds wearing personalized audio delivery devices such as headphones, hearables, earbuds, speakers, or hearing aids. The personalized audio delivery devices outputs sound, e.g., music, into the ear canal of the outer ear. For example, a user wears an earcup seated on the pinna which outputs the sound into the ear canal. Alternatively, a bone conduction headset vibrates middle ear bones to conduct the sound to the human auditory system. The personalized audio delivery devices accurately reproduce sound. But unlike sound from a sound source, the sound from the personalized audio delivery devices does not interact with the human anatomy such that direction where the sound is coming from is accurately perceptible. The seating of the earcup on the pinna prevents the sound from the personal audio delivery device from interacting with the pinna and the bone conduction may bypass the pinna altogether. Audio cues indicative of direction is not generated and as a result the person is not able to perceive the direction where the sound is coming from.